1. Field of the Invention
The present invention relates in general to concrete saws. In particular, the present invention relates to an improved saw for the grooving of uncured or green, in addition to cured concrete to aid in crack control.
2. Description of the Related Art
It has been known for many years to provide grooves in concrete for crack control. The formation of the groove in the o concrete provides an area of reduced strength to ensure that the cracks which form during shrinkage of the concrete will be formed along the line of the groove rather than at some other point. This has important structural implications, in addition to providing a more aesthetically pleasing appearance.
The traditional method of forming grooves was to manually form the groove by use of a trowel. This is a time consuming process which requires a fair amount of skill. Additionally, since this must be performed when the concrete is recently poured, the concrete will not support the weight of the laborer forming the grooves. This makes it especially difficult to form grooves across large slabs of concrete is to cut the grooves with a rotating saw blade. The Guide for Concrete Floor and Slab Construction, American Concrete Institute, No. ACI 302.1R-80 (hereinafter "ACI Guide") shows that such grooves should be cut when it has hardened sufficiently to support a worker with at most a 1/4 inch foot indention in the concrete surface, but before the concrete has dried sufficiently to cause random cracking, and that this requires the concrete to be cut within 4 to 12 hours after finishing. The ACI Guide also teaches that the grooves should be cut as soon as possible, with raveling of the edges and dislodging aggregate being the limiting factors as to how soon cutting may take place.
Various patents, such as U.S. Pat. No. 2,854,043 to Raymond and U.S. Pat. No. 3,623,518 to Nicotra teach the use of skid plates which contact the work surface closely adjacent counter rotating blades to reduce ravelling of the cut edges. U.S. Pat. No. 2,673,725 to Coates and U.S. Pat. No. 2,700,256 to Lewis disclose pivotal and biased mounting of concrete cutting blades to permit the blade to pass over obstructions in the concrete.
A light weight saw having such a skid plate and pivotally biased blade.
An alternative method of forming grooves in concrete has been proposed in U.S. Pat. No. 4,769,201 to Chiuminatta, et al. This patent teaches the cutting of a groove in partially cured concrete which may not be walked upon (i.e. the worker would sink greater than the 1/4 inch depth allowed in the ACI Guide), and therefore much less than 4 hours after finishing. This method of forming grooves has advantages over the manual trowel method, but has suffered from several drawbacks. The commercial form of the device shown in this patent must employ a special "ramp" to start the saw in the grooving operation. Additionally, the saw rests upon a skid plate which makes it difficult for the user to move the saw forward, and which may damage the surface of the uncured concrete. Also, the saw blade is raised out of the formed groove by rotation of a handle used to push the saw. This rotation is about the longitudinal axis of the handle and tends to rotate the saw and thus the cutting blade about an axis perpendicular to the cutting rotation of the saw blade, moving the saw off the desired line and widening the groove. Finally, the long handles removably mounted to the saw are often misplaced or not supplied with the saw, rendering it inoperative until a handle is supplied.